From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 839B06B0005 for ; Mon, 11 Jun 2018 21:23:25 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id y26-v6so11124730pfn.14 for ; Mon, 11 Jun 2018 18:23:25 -0700 (PDT) Received: from mga12.intel.com (mga12.intel.com. [192.55.52.136]) by mx.google.com with ESMTPS id q14-v6si18809650pll.324.2018.06.11.18.23.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Jun 2018 18:23:23 -0700 (PDT) From: "Huang\, Ying" Subject: Re: [PATCH -mm -V3 03/21] mm, THP, swap: Support PMD swap mapping in swap_duplicate() References: <20180523082625.6897-1-ying.huang@intel.com> <20180523082625.6897-4-ying.huang@intel.com> <20180611204231.ojhlyrbmda6pouxb@ca-dmjordan1.us.oracle.com> Date: Tue, 12 Jun 2018 09:23:19 +0800 In-Reply-To: <20180611204231.ojhlyrbmda6pouxb@ca-dmjordan1.us.oracle.com> (Daniel Jordan's message of "Mon, 11 Jun 2018 13:42:31 -0700") Message-ID: <87o9ggpzlk.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: owner-linux-mm@kvack.org List-ID: To: Daniel Jordan Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Andrea Arcangeli , Michal Hocko , Johannes Weiner , Shaohua Li , Hugh Dickins , Minchan Kim , Rik van Riel , Dave Hansen , Naoya Horiguchi , Zi Yan Hi, Daniel, Thanks for your effort to review this series. Daniel Jordan writes: > Hi, > > The series up to and including this patch doesn't build. For this patch we > need: > > diff --git a/mm/swap_state.c b/mm/swap_state.c > index c6b3eab73fde..2f2d07627113 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -433,7 +433,7 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, > /* > * Swap entry may have been freed since our caller observed it. > */ > - err = swapcache_prepare(entry); > + err = swapcache_prepare(entry, false); > if (err == -EEXIST) { > radix_tree_preload_end(); > /* Thanks for pointing this out! Will change in the next version. > > On Wed, May 23, 2018 at 04:26:07PM +0800, Huang, Ying wrote: >> @@ -3516,11 +3512,39 @@ static int __swap_duplicate(swp_entry_t entry, unsigned char usage) > > Two comments about this part of __swap_duplicate as long as you're moving it to > another function: > > } else if (count || has_cache) { > > if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) /* #1 */ > count += usage; > else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) /* #2 */ > err = -EINVAL; > > #1: __swap_duplicate_locked might use > > VM_BUG_ON(usage != SWAP_HAS_CACHE && usage != 1); > > to document the unstated assumption that usage is 1 (otherwise count could > overflow). Sounds good. Will do this. > #2: We've masked off SWAP_HAS_CACHE and COUNT_CONTINUED, and already checked > for SWAP_MAP_BAD, so I think condition #2 always fails and can just be removed. I think this is used to check some software bug. For example, SWAP_MAP_SHMEM will yield true here. >> +#ifdef CONFIG_THP_SWAP >> +static int __swap_duplicate_cluster(swp_entry_t *entry, unsigned char usage) > ... >> + } else { >> + for (i = 0; i < SWAPFILE_CLUSTER; i++) { >> +retry: >> + err = __swap_duplicate_locked(si, offset + i, 1); > > I guess usage is assumed to be 1 at this point (__swap_duplicate_locked makes > the same assumption). Maybe make this explicit with > > err = __swap_duplicate_locked(si, offset + i, usage); > > , use 'usage' in cluster_set_count and __swap_entry_free too, and then > earlier have a > > VM_BUG_ON(usage != SWAP_HAS_CACHE && usage != 1); > > ? Yes. I will fix this. And we can just check it in __swap_duplicate_locked() and all these will be covered. >> +#else >> +static inline int __swap_duplicate_cluster(swp_entry_t *entry, > > This doesn't need inline. Why not? This is just a one line stub. > Not related to your changes, but while we're here, the comment with > SWAP_HAS_CONT in swap_count() could be deleted: I don't think there ever was a > SWAP_HAS_CONT. Yes. We should correct this. Because this should go to a separate patch, would you mind to submit a patch to fix it? > The rest looks ok up to this point. Thanks! Best Regards, Huang, Ying